Piezoelectric light-emitting diode and backlight system using the same
A light-emitting diode (LED) (10) includes a chip body (103), an encapsulation can (105) surrounding the chip body, and a base (106) supporting the encapsulation can and the chip body thereon. Numerous diffusion structures (1050) are provided on the encapsulation can, and the encapsulation can is made of a piezoelectric material for widening radiation angles of light beams emitted from the chip body. With the diffusion structures and the piezoelectric encapsulation can, light beams from the chip body are diffused and attain wider radiation angles. A backlight system (900) includes a light guide plate (20), and a number of the above-described LEDs disposed adjacent to the light guide plate. Light beams having wide radiation angles are emitted from the LEDs and enter the light guide plate. This enables a light emitting surface of the light guide plate to have highly uniform brightness.
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1. Field of the Invention
The present invention relates to light-emitting diodes (LEDs), and especially to an LED used in a backlight system for a device such as a liquid crystal display.
2. Description of the Prior Art
Liquid crystal displays are commonly used as the display device for compact electronic apparatuses, because they not only display good quality images using little power but also are very thin. However, the liquid crystals in a liquid crystal display do not emit any light themselves. The liquid crystals have to be lit up by a light source so as to clearly and sharply display text and images. Typically, LEDs are used as the light source because of their high luminance and low loss.
Referring to
Therefore, it is desired to provide an LED and a backlight system using the same which overcome the above-described disadvantages of the prior art.
SUMMARY OF THE INVENTIONAn object of the present invention is to provide an LED which has a large radiation angle.
Another object of the present invention is to provide a backlight system yielding uniform illumination derived from light beams originally emitted from one or more LEDs having large radiation angles.
According to a first aspect of the present invention, there is provided an LED comprising a chip body, an encapsulation can surrounding the chip body, and a base supporting the encapsulation can and the chip body thereon. A plurality of diffusion structures is provided on the encapsulation can, and the encapsulation can is made of a piezoelectric material for widening radiation angles of light beams emitted from the chip body.
According to a second aspect of the present invention, there is provided a backlight system comprising a light guide plate, and a plurality of LEDs according to the above-described LED. The LEDs are disposed adjacent to the light guide plate. Light beams having wide radiation angles are emitted from the LEDs and enter the light guide plate. This enables a light emitting surface of the light guide plate to have highly uniform brightness without any dark areas.
Other objects, advantages, and novel features of the present invention will be apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to
The light guide plate 20 is made of a transparent material such as acrylic resin, polycarbonate resin, polyvinyl chloride, or glass. The light guide plate 20 is a rectangular sheet, or alternatively may be generally cuneiform. The light guide plate 20 includes a light incident surface 201, an emitting surface (not labeled) connected with the light incident surface 201, and a bottom surface 203 opposite to the emitting surface. The light incident surface 201 of the light guide plate 20 receives light beams from the LEDs 10. The emitting surface of the light guide plate 20 is flat, and the bottom surface 203 of the light guide plate 20 can be formed with a plurality of dots 207. The dots 207 improve the uniformity of illumination of the light guide plate 20. Sizes of the dots 207 become progressively larger with increasing distance away from the light incident surface 201. The dots 207 may for example be hemispherical, cylindrical, cubic, cuboid, or pyramidal. In the illustrated embodiment, hemispherical dots 207 are used. Alternatively, the bottom surface 203 of the light guide plate 20 can be formed with V-cut grooves (not shown) instead of with the dots 207.
Referring to
The encapsulation can 105 is made of a transparent piezoelectric material, such as a transparent piezoelectric ceramic. The encapsulation can 105 is connected to an electrical controlling circuit (not shown) to control the deformation of the encapsulation can 105. Because the encapsulation can 105 is made of the piezoelectric material, that has the characteristic of electromechanical coupling, the encapsulation can 105 induced to mechanically deform when an electric field is applied. When the controlling circuit is operated so that an electric field is applied on the encapsulation can 105, the dipole moment of the piezoelectric material of the encapsulation can 105 extends along the direction of the electric field.
When an electric field (not shown) is applied on the encapsulation can 105, the encapsulation can 105 is induced to deform. P, L and θ of the V-shaped grooves 1050 vary according to the voltage used to generate the electric field. θ increases with increasing voltage. In such case, more light beams can pass through the V-shaped grooves 1050.
Referring to
In summary, by providing the V-shaped grooves 1050 on the encapsulation can 105, light beams emitted from the chip body 103 are diffused. Further, the encapsulation can 105 can be induced to deform by application of an electric field, thereby, controlling widening of the radiation angle of the LED 10. This improves the uniformity of illumination provided by the backlight module 900.
Many modifications and variations are possible within the ambit of the invention herein. For example, the V-shaped grooves 1050 can instead be Fresnel lenses or convex protrusions. More than one chip body 103 may be provided in each LED 10. The backlight system 900 may further include a diffusion sheet and a prism sheet. All such and other modifications and variations that may be apparent to a person of ordinary skill in the art are intended to be within the scope of the present invention.
It is to be further understood that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Claims
1. A light-emitting diode comprising:
- a base;
- a chip body fixed on the base for emitting light beams; and
- an encapsulation can covering the chip body;
- wherein a plurality of diffusion structures is provided at a surface of the encapsulation can, and the encapsulation can is made of a piezoelectric material such that radiation angles of light beams passing through the diffusion structures can be widened.
2. The light-emitting diode as claimed in claim 1, wherein the diffusion structures comprise V-shaped grooves.
3. The light-emitting diode as claimed in claim 2, further comprising an electrical circuit connected with the encapsulation can for controlling the deformation of the encapsulation can.
4. The light-emitting diode as claimed in claim 2, wherein a vertex angle of each V-shaped grooves is in the range from 70˜140°.
5. The light-emitting diode as claimed in claim 2, wherein a distance separating each two V-shaped grooves is in the range from 10 to 350 μm.
6. The light-emitting diode as claimed in claim 1, wherein the diffusion structures are Fresnel lenses.
7. The light-emitting diode as claimed in claim 1, wherein the diffusion structures are convex protrusions.
8. The light-emitting diode as claimed in claim 1, wherein the encapsulation can is made of a piezoelectric ceramic.
9. A backlight system comprising:
- at least one light-emitting diode comprising a base,
- a chip body mounted on the base for emitting light beams, and
- an encapsulation can mounted on the base, wherein a plurality of diffusion structures provided at a surface of the encapsulation can, and the encapsulation can made of a piezoelectric material such that radiation angles of light beams passing through the diffusion structures can be widened; and
- a light guide plate comprising a light incident surface adjacent to the diffusion structures in order to receive light beams therefrom, and a light exit surface.
10. The backlight system as claimed in claim 9, wherein the diffusion structures comprise V-shaped grooves.
11. The backlight system as claimed in claim 10, wherein a circuit connected with the encapsulation can for controlling the deformation of the encapsulation can.
12. The backlight system as claimed in claim 10, wherein a vertex angle of each V-shaped grooves is in the range from 70˜140°.
13. The backlight system as claimed in claim 10, wherein a distance separating each two adjacent V-shaped grooves is in the range from 10 to 350 μm.
14. The backlight system as claimed in claim 9, wherein the diffusion structures are Fresnel lenses.
15. The backlight system as claimed in claim 9, wherein the diffusion structures are convex protrusions.
16. The backlight system as claimed in claim 9, wherein the encapsulation can is made of a piezoelectric ceramic.
17. A backlight system comprising:
- a light source;
- a light guide member comprising a light incident surface facing said light source so as to allow light from said light source passable through said incident surface into said light guide member for transmission of said light guide member; and
- a diffusion structure extendable between said light source and said incident surface of said light guide member, and interferingly disposed around said light source to diffuse all of said light from said light source.
18. The backlight system as claimed in claim 17, wherein said diffusion structure is stretchable in case of electrification.
19. The backlight system as claimed in claim 17, wherein said diffusion structure is made of piezoelectric ceramic.
20. The backlight system as claimed in claim 17, wherein said diffusion structure comprises a continuous-V-shaped-groove surface.
Type: Application
Filed: Sep 27, 2004
Publication Date: Apr 28, 2005
Patent Grant number: 7175328
Applicant: HON HAI Precision Industry CO., LTD. (Tu-Cheng City)
Inventors: Charles Leu (Fremont, CA), Ga-Lane Chen (Fremont, CA), Tai-Cherng Yu (Tu-Cheng)
Application Number: 10/951,845